1. Field of the Invention
The present invention relates to the field of disk drives, and in particular, to a microactuator for finely positioning a read/write head of a hard disk drive and a suspension arrangement of the hard disk with the microactuator.
2. Description of the Related Art
A disk drive is an information storage device that uses a rotatable disk with data tracks, a magnetic head (SLD [slider]) for reading or writing data from or onto the tracks, and an actuator connected to a carrier for moving the head across the disk. A servo system receives prerecorded positioning information read from the disk by the head, and sends control signals to the actuator to move the head to the desired track and keep following it when the head is flying.
The SLD flying over information tracks of the disks is mounted on a suspension of the actuator, which has a load beam with a base plate on one end (proximal end), and a flexure on the other end (distal end) on one end (proximal end), and a flexure on the other end (distal end) on which the SLD is located. There is a spring region near the base plate on the load beam, the thickness of which is thinner than that of other areas, -producing a force to help maintain the flying SLD stability. The base plate of the suspension is mounted to the actuator arm, which is controlled by the servo system to position the SLD. A similar mechanism for minute movement of a head used in a disk drive is disclosed in U.S. Pat. No. 5,764,444 issued on Jun. 9, 1998, to Takahiro Imamura et al, and assigned to Fujitsu Limited. However, this mechanism is unable to precisely control the displacement of the head with a high efficiency.
Since the disk storage capacity is increasing all of the time, it becomes more difficult for the actuator and servo system to position the SLD over the desired track quickly and accurately. Many kinds of microactuator or fine tracking motors have been developed to overcome these problems, which are called as dual stage systems since the microactuators are added to the suspensions and will work with the previous actuators together.
Recently, piezoelectric materials are used more and more in microactuators that can extend or contract under a certain voltage with high efficiency. There are two kinds of suspension arrangements for the piezoelectric microactuator in current dual stage servo system designs. One is suspension type: the microactuator is mounted on the proximal end of the suspension (near the spring region ); another is SLD type the microactuator is mounted on the distal end of the suspension, between the SLD and flexure (called a piggy back design).
The challenges in microactuator design on the suspension are: the SLD should get a big lateral displacement under control of the dual stage servo system, the suspension assembly with a microactuator should keep the resonance frequency as high as possible and the strength as strong as possible and should not affect the SLD flying.